1. Field of the Invention
The present invention relates to a thin film magnetic head having at least an inductive magnetic transducer for writing and a method of manufacturing the same.
2. Description of the Related Art
In recent years, improvement in performance of a thin film magnetic head is demanded in association with improvement in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head in which a recording head having an inductive magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinbelow, referred to as MR) device for reading are stacked is widely used. MR devices include an anisotropic magnetoresistive (hereinbelow, described as AMR) device using the AMR effect and a GMR (giant magnetoresistive) device using the GMR effect. A reproducing head using the AMR device is called an AMR head or simply an MR head. A reproducing head using the GMR device is called a GMR head. The AMR head is used as a reproducing head having a surface recording density which is higher than 1 Gbit/inch2. The GMR head is used as a reproducing head whose surface recording density is higher than 3 Gbits/inch2.
The AMR film is a film made of a magnetic substance producing the MR effect and has a single layer structure. On the other hand, many of GMR films have a multi-layer structure in which a plurality of films are combined. There are some kinds of mechanisms of producing the GMR effect. The layer structure of the GMR film varies according to the mechanism. As GMR films, a super lattice GMR film, a spin valve film, a granular film, and the like have been proposed. The spin valve film is promising as a GMR film having a relatively simple construction and exhibiting a large resistance change with a weak magnetic field, which is intended for mass production.
A factor of determining the performance of the reproducing head is processing accuracy of a pattern width, especially, an MR height. The MR height is the length (height) from the end on the air bearing surface (ABS) side of the MR device to the end on the opposite side, and is inherently controlled by a polishing amount at the time of processing the air bearing surface. The air bearing surface is a surface of a thin film magnetic head, which faces a magnetic recording medium, and is also called a track surface.
On the other hand, in association with the improvement in performance of a reproducing head, improvement in performance of a recording head is also demanded. In order to increase the recording density in the performance of the recording head, it is necessary to raise the track density in a magnetic recording medium. For this purpose, it is necessary to realize a recording head of a narrow track structure in which the track width on the air bearing surface of each of a bottom pole and a top pole formed while sandwiching a write gap is reduced to the order of a few microns to submicrons. In order to achieve this, semiconductor processing techniques are used.
Another factor of determining the performance of the recording head is processing accuracy of the throat height (TH). The throat height is the length (height) of a portion (magnetic pole portion) extending from the air bearing surface to the edge of an insulating layer which electrically isolates a thin film coil. In order to improve the performance of the recording head, reduction in the throat height is desired. The throat height is also controlled by a polishing amount at the time of processing the air bearing surface.
In order to improve the performance of a thin film magnetic head, it is important to form the recording head and a reproducing head as described above with a good balance.
Referring now to FIGS. 30A and 30B to FIGS. 35A and 35B, a method of manufacturing a composite thin film magnetic head as an example of a conventional thin film magnetic head will be described. FIG. 36 is a plan view of a conventional composite thin film magnetic head. FIGS. 30A to 35A are cross sections each taken along cut line XXXVAxe2x80x94XXXVA of FIG. 36. FIGS. 30B to 35B are process cross sections each taken along cut line XXXVBxe2x80x94XXXVB of FIG. 36.
First, as shown in FIGS. 30A and 30B, an insulating layer 102 made of, for example, alumina (aluminium oxide, Al2O3) is formed in thickness of about 5 to 10 xcexcm on a substrate 101 made of, for example, altic (Al2O3.TiC). Subsequently, a bottom shield layer 103 for a reproducing head made of permalloy (NiFe) or the like is formed on the insulating layer 102.
As shown in FIGS. 31A and 31B, for example, alumina is then formed in thickness of 100 nm to 200 nm on the bottom shield layer 103 to form a shield gap film 104. An MR film 105 for constructing an MR device for reproduction is deposited in thickness of tens nm on the shield gap film 104 and is formed in a desired shape by high-precision photolithography. Then a pair of lead terminal layers 106 are formed on both ends of the MR film 105 by a lift-off method. A shield gap film 107 is formed on the shield gap film 104, MR film 105, and lead terminal layers 106 and the MR film 105 and the lead terminal layers 106 are buried between the shield gap films 104 and 107. A top shield-cum-bottom pole (hereinbelow, simply described as bottom pole) 108 having a thickness of 3 xcexcm made of a magnetic material such as NiFe used for both the reproducing head and the recording head is formed on the shield gap film 107.
As shown in FIGS. 32A and 32B, on the bottom pole 108, a write gap layer 109 having a thickness of 200 nm as an insulating film which is, for example, an alumina film is formed. Further, the write gap layer 109 is patterned by photolithography and an opening 109A for connecting the bottom pole 108 and a top pole (116) which will be formed later on the write gap layer is formed. Subsequently, a pole tip 110 is formed by using a magnetic material such as NiFe or iron nitride (FeN) by plating and a poles coupling portion 110A for magnetically connecting the top pole and the bottom pole 108 is formed. By preliminarily forming the poles coupling portion 110A, the bottom pole 108 and the top pole can be easily magnetically connected to each other without forming an opening (through hole) for connecting both of the poles after forming an insulating layer 111 and planarizing the surface of the insulating layer 111 by a CMP (Chemical and Mechanical Polishing) process.
As shown in FIGS. 33A and 33B, the pole tip 110 is used as a mask and etching of about: 0.3 to 0.5 xcexcm is performed by ion milling to remove a part of the surfaces of the write gap layer 109 and the bottom pole 108. Etching is performed to the bottom pole 108 and a trim structure is obtained, thereby preventing the effective write track width from being expanded (that is, the expansion of a magnetic flux in the bottom pole 108 is suppress at the time of writing data). Subsequently, the insulating layer 111 made of, for example, alumina having a thickness of about 3 xcexcm is formed on the whole surface of the substrate and the whole surface of the insulating layer 111 is planarized by CMP.
As shown in FIGS. 34A and 34B, a thin film coil 112 as the first layer for an inductive recording head made of, for example, copper (Cu) is selectively formed on the insulating layer 111 by plating or the like. Subsequently, a photoresist film 113 is formed in a predetermined pattern by high-precision photolithography on the insulating layer 111 and the thin film coil 112. Then, heat treatment is performed at a predetermined temperature for planarizing the photoresist film 113 and insulating t urns of the thin film coil 112. Further, under conditions similar to those of the first thin film coil 112, a thin film coil 114 as the second layer is formed on the photoresist film 113. A photoresist film 115 is formed on the second thin film coil 114 and heat treatment is performed at a predetermined temperature for planarizing the photoresist film 115 and insulating the turns of the thin film coil 114 from each other.
As shown in FIGS. 35A and 35B, a top yoke-cum-top pole (hereinbelow, simply described as top pole) 116 made of a magnetic material such as NiFe for the recording head is formed on the pole tip 110 and the photo resist films 113 and 115. As shown in FIG. 36, the top pole 116 is in contact with and magnetically coupled to the bottom pole 108 via the poles coupling portion 110A in the center portion of each of the thin film coils 112 and 114. Subsequently, an overcoat layer 117 made of, for example, alumina is formed on the top pole 116 (refer to FIGS. 35A and 35B). Finally, by machining a slider, the track surface (air bearing surface) 118 of the recording head and reproducing head is formed, thereby completing a thin film magnetic head.
In FIGS. 35A and 35B and FIG. 36, reference characters TH denote the throat height and MR-H indicates the MR height. Reference numeral P2W shows the track (pole) width. A factor of determining the performance of the thin film magnetic head other than the throat height TH, the MR height MR-H, and the like is an apex angle xcex8 shown in FIG. 35A. The apex angle xcex8 is formed between the straight line connecting the corners of side faces on the track face sides of the photoresist films 113 and 115 and the top face of the top pole 116.
It is presumed that the surface recording density of a thin film magnetic head of this kind will reach as high as 10 Gbits/inch2 to 20 Gbits/inch2 in near future and will be used in a high frequency band of 300 MHz to 500 MHz. It is an important issue to optimally assure a magnetic volume around a position where the throat height TH is zero.
As a matter of course, when a large magnetic volume is obtained around the position where the throat height TH is zero, the overwrite characteristic can be improved. Japanese Unexamined Patent Application No. 2000-105907 discloses a top pole having spread of 90 degrees from the track width P2W near the position where the throat height TH is zero and clarifies that the overwrite write characteristic is easy to be improved by such a top pole.
In the case where a magnetic flux is concentrated around the position where the throat height TH is zero, a large amount of the magnetic flux leaks from the pole tip to a magnetic recording medium. Consequently, a problem such as side write that recording data is written on a recording track next to a recording track to which recording data is inherently to be written and spreading of the recording track width on a magnetic recording medium often occurs.
Further, in a thin film magnetic head, when a magnetic flux flows excessively from the pole tip and the flow of the magnetic flux is regulated extremely around the air bearing surface, a trouble such that the magnetic effective write track width in a low frequency characteristic and that in a high frequency characteristic are extremely different from each other often occurs. When an excessive magnetic flux flows to a portion around the air bearing surface, a trouble such that xe2x80x9cside track erasexe2x80x9d of erasing recording data which has been already written in a recording track next to a recording track to which recording data is to be written often occurs. Particularly, in a thin film magnetic head assembled in a hard disk drive, when a magnetic disk is skewed laterally, the side track erase often occurs in the center or peripheral area of the magnetic disk.
The invention has been achieved in consideration of the problems and its first object is to provide a thin film magnetic head capable of optimally controlling a magnetic flux flowing in a pole (pole tip) and a magnetic layer (capable of performing an optimal flux control) and a method of manufacturing the same.
A second object of the invention is to provide a thin film magnetic head capable of improving an overwrite characteristic by avoiding saturation of a magnetic flux and assuring supply of a sufficient magnetic flux to a pole and capable of preventing inconveniences such as side write, spreading of the recording track width, and side track erase by suppressing a flow of an excessive magnetic flux to a pole and a method of manufacturing the thin film magnetic head.
A third object of the invention is, while achieving the second object of the invention, to provide a thin film magnetic head capable of reducing an amount of a difference between magnetic effective write track widths due to different frequency characteristics and a method of manufacturing the same.
Further, a fourth object of the invention is to provide a thin film magnetic head capable of achieving at least any one of the first to third objects by a simple structure or a simple manufacturing method and a method of manufacturing the same.
Further, a fifth object of the invention is to provide a thin film magnetic head capable of achieving the first to fourth objects while reducing the number of manufacturing steps and a method of manufacturing the same.
According to the invention, there is provided a thin film magnetic head including: two magnetic layers magnetically coupled to each other and having two magnetic poles which face each other with a gap layer in between in part close to a recording-medium-facing surface facing a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, wherein a nonmagnetic area is formed in at least one of the two magnetic layers.
According to the invention, there is provided a method of manufacturing a thin film magnetic head including: two magnetic layers magnetically coupled to each other and having two magnetic poles which face each other with a gap layer in between in part close to a recording-medium-facing surface facing a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, the method comprising the steps of forming the two magnetic layers; and forming a nonmagnetic area in at least one of the two magnetic layers.
In a thin film magnetic head or a method of manufacturing the same according to the invention, the nonmagnetic area exists in at least one of the two magnetic layers, so that the magnetic flux cannot pass the nonmagnetic area. That is, the nonmagnetic area functions as a kind of an obstacle for the flow of the magnetic flux.
In a thin film magnetic head or a method of manufacturing the same according to the invention, especially, when the xe2x80x9cnonmagnetic areaxe2x80x9d is disposed in a position close to the pole portion, the magnetic flux flowing from the portion except for the pole portion to the pole potion can be effectively controlled. The xe2x80x9cnonmagnetic areaxe2x80x9d can be constructed so as to have a hole formed in the magnetic layers and the nonmagnetic area is formed as a nonmagnetic body buried in the hole. The xe2x80x9cholexe2x80x9d includes not only a through hole which completely penetrates the magnetic layer but also a bottomed hole having a part of the magnetic layer on the bottom. The width of the hole is, preferably, wider than the width of the magnetic poles and narrower than the width of the magnetic layer other than the magnetic poles.
The xe2x80x9cnonmagnetic areaxe2x80x9d can be made of a material including at least one of an insulating material or a conductive material. It is preferable to form the xe2x80x9cnonmagnetic areaxe2x80x9d in a central portion in the width direction of the magnetic layer. In this case, the magnetic flux flowing to the pole portion is once received and the force of the flow is lessened. More preferably, the received magnetic flux is shunted so as to detour the nonmagnetic area, merged again, and be led to the pole portion.
In the thin film magnetic head or the method of manufacturing the same according to the invention, preferably, an edge position opposite to the recording-medium-facing surface, of at least one of the two magnetic poles, coincides with an edge position close to the recording-medium-facing surface, of the insulating layer, and the nonmagnetic area is disposed in a neighbor of the edge opposite to the recording-medium-facing surface, of the magnetic poles.
Preferably, in the method of manufacturing the thin film magnetic head according to the invention, the step of forming the nonmagnetic area includes: a step of forming a hole in at least one of the magnetic layers; and a step of burying a nonmagnetic body in the hole. In this case, for example, when the hole is formed upon formation of the magnetic layer and the nonmagnetic area is formed by burying the same insulating material in the hole upon deposition of the insulating material covering the magnetic layer, the nonmagnetic area is formed by using the process of forming the magnetic layer and the process of depositing the insulating material. Thus, a process especially for forming the nonmagnetic area is not needed.
In the thin film magnetic head or the method of manufacturing the same according to the invention, at least one of the magnetic layers includes: one of the two magnetic poles; and a yoke integrated with and magnetically coupled to the one of the two magnetic poles so as to extend to an area in which the thin film coil is formed. In this case, it can be constructed that the one of the poles and the yoke are formed in the single layer and the nonmagnetic area is disposed in a part of the yoke. It is also possible to form the one of the poles and the yoke in different layers and dispose the nonmagnetic area in a part of the yoke portion. It is also possible to form the one of the poles and the yoke separately and dispose the nonmagnetic area in a part of one of the pole portions.
According to the invention, there is provided another thin film magnetic head including: two magnetic layers magnetically coupled to each other and having two magnetic poles which face each other with a gap layer in between in part close to a side of a recording-medium-facing surface; and a thin film coil disposed between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, wherein in at least one of the two magnetic layers, a magnetic flux control portion for controlling the flow of a magnetic flux in the at least one of the magnetic layers is provided.
According to the invention, there is provided a method of manufacturing another thin film magnetic head having: two magnetic layers magnetically coupled to each other and having two magnetic poles which face each other with a gap layer in between in part close to a recording-medium-facing surface facing a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, comprising the steps of: forming the two magnetic layers; and forming a magnetic flux control portion for controlling the flow of a magnetic flux in at least one of the two magnetic layers.
In the above. cases, it is preferable to dispose the magnetic control portion in a position close to the pole portion.
Other and further objects, features and advantages of the invention will appear more fully from the following description.